Requests for audio drama don't seem to have a specific section on the forum, but since this is based on a tv show you might try
Forum: TV/Movie Discussion
http://forums.ffshrine.org/forumdisplay.php?f=76
or
Forum: General Discussion
http://forums.ffshrine.org/forumdisplay.php?f=2
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Just noticed the list of "Sapphire & Steel" audio dramas at
https://en.wikipedia.org/wiki/List_of_Sapphire_%26_Steel_serials#Audio_serials
can be found in an mp3 download (1.6G) at
https://www.ulozto.net/!USyUUmFlmeTe/sapphire-and-steel-zip .
Also try at
https://my-free-mp3s.com/mp3juices . Type Sapphire & Steel in search section and you should get files that look like
"Sapphire & Steel - S&S3.2 Remember Me CD1 my-free-mp3s.com." They're not in order but seem to all be there.
Hope this helps.